A client of mine has a product that is powered at 24Vdc or 24Vac. Among other features, the unit has an RS485 port.
A number of units were submitted to a certification lab in China. Upon performing the EFT test, all failed with some components melted and in one case going missing from the PCB.
Here is the input power circuitry:
where TVS10 is SMBJ36CA and the F116 is a PTC fuse 1.1A from Bell Fuse Inc.
Here are some pictures showing the amount of destruction:
and for RS485, you can see F32 disapeared completely
Does this unit powered at 24V needs a test with so much energy ?
The unit power consumption is under 5W.